text:
What happened with flight AC692 to St John's?
Yesterday, 2nd of March 2020, I was on board of Air Canada flight AC692 from Toronto (YYZ) to St. Johns (YYT). 40 minutes before landing, the plane turned around and flew back to Toronto. The flight time was supposed to be 2:20 hours, instead we flew a round of ~4 hours. The pilot announced that it "unsafe to land" in St John's. But this sounds rather ambiguous to me.
I have a colleague in St John's. He says the there was quite a bit of snow in the morning, but by the time we were in the air, all the roads were clean. This mean they easily could have cleared the runway? Overall conditions weren't too bad and the sky was clear with sun.
Wind would be another condition, but this was a Boeing 777. Those can handle a bit of wind conditions, as opposed to the smaller aircraft types?

Why all the way back to Toronto? Why not divert to Halifax or Montreal and wait until the conditions get better?
I was in the understanding planes don't over-fuel for safety reasons. How did we make it back to Toronto without refueling? If we wouldn't have turned back, would the plane have had too much fuel to land?

I would like to add during the landing in Toronto, flaps were pulled down rather late to my experience. The approach was rather short (in time) and spoilers were used during descend. Also, (almost) no reverse thrust was used used during braking. Does this tell me the plane was running on fumes?

the METAR from 02/03/2020 20:00UTC (5 minutes after the turn-around): METAR CYYT 022000Z 01019G27KT 15SM -SN OVC009 M04/M06 A2983 RMK SF8 SLP110=

Of all of the questions like this we get on this site, I’ll admit that this is the best one I’ve seen in a while.  Very detailed and light on speculation.  +1.  Keep ‘em coming!

To decipher the previous METAR: wind was from ~north at 19kts, strong gusts (27kts), good visibility, light snowfall. The thing is, the wind and gusts are pretty much perpendicular to the main runway. Still I don't think that's too much for a 777 + a competent pilot.

The Runway Surface Condition could have been the reason for the diversion. The B777 is a large, HEAVY aircraft that needs lots of runway, and good braking conditions to stop.  Any amount of crosswind just magnifies these challenges.

Why return to Toronto and not stop on the way:

Generally speaking the most probable cause for reverting back to an airport that seems an unlikely choice is that the airline has a base there. From a base airport the aircraft is readily available for other use, and crew rotations are easily managed. In addition to that, if the "unsafe to land" condition was due to a technical issue with the plane, maintenance is secured at a base airport, but not necessarily elsewhere.
As Verandaguy pointed out in his comment, Air Canada does have a base at Montreal, which would have been closer to the aircraft at the time of diverting. This being the case, the reason for returning to Toronto is very likely to get the plane and crew to a position that best suits  the following rotation of each.
We do not know about the flight hours the crew had on them, so diverting to a non-base or non-scheduled airport might have caused serious trouble with continuation of the flight: You might have to fly (or if diverted to a base, call up) a relief crew to the divert airport  to fly the plane onward, and the crew with rest period limitation would have to be flown to their "home" base airport. This situation might have arisen at St. Johns after a stopover enroute.
While I at first did not think that weather was the reason (ref. METAR posted by Federico), it turned out that runway conditions were not suitable for landing in high and gusting crosswind (comment below by Mike Sowsun, kudos for that). We do not know the weather trend, so flying to, say, Halifax might prove problematic if the weather and/or runway conditions did not get better fast enough (see previous bullet point)

Fuel: too much to land at destination, too little on arrival at Toronto?

The reason for not carrying extra fuel is pretty much solely economical: it's a huge waste of money to fly fuel around instead of cargo or passengers. However, while it is true that airlines do not like to ferry extra fuel, an aircraft has all sorts of reserve fuel on board: you carry extra juice for trip to alternate airport, holding at destination or alternate and so on. When a crew decides to divert to an alternate airport, they make sure they choose one that does not result in fuel emergency.
It is therefore extremely unlikely that the plane was running on fumes when it arrived at Toronto.
Nor is it likely at all that the plane would have been over fueled by mistake. If it had been so, you would most probably just have circled at St. Johns for a while to burn the excess off, or dumped on the way there.
The observed use of flaps and/or speed brakes cannot be used to determine the fuel situation of the plane. These are more likely dictated by traffic situation.

As for the reasons for not landing at intended destination: As Mike Sowsun commented below, runway conditions were less than satisfactory, and the captain made the only possible judgement call: high gusty crosswind + slippery runway is a big no-no. A roadside observation cannot be used as a reference when judging what conditions are at an airport, even nearby. I know by experience that local variations in weather can be huge at places such as St. Johns. Also, changes in weather at these latitudes in coastal regions are very hard to predict, sometimes even for such short periods of time as the duration of this flight.

When you combine the crosswind on Runway 11 with the runway conditions, it is very easy to see why the Captain chose not attempt a landing. You can hear the Runway Surface Condition Report for that period LiveATC.net: "CYYT Runway Surface Conditions for Runway 11 at 17:50z:  Center 160' of the runway, 60% wet snow covered 1/8", 25% bare and damp, 15% compact snow. Outside the center-line : 95% wet snow 3 inches in depth, 5% wet snow over ice, 3 inches in depth." (starting at 03:50) https://archive-server.liveatc.net/cyyt/CYYT1-Gnd-Mar-02-2020-2000Z.mp3

@MikeSowsun very nice find! That would make an answer on it's own I think, as reason for diversion was also kind of asked in the question.

Worth mentioning that ACA has a base and corporate headquarters at (and very nearby, respectively) CYUL.

Thanks @verandaguy, I'll have to update my answer with that when I have a couple more minutes to spare.

Given the flight was only two and a half hours long, were these conditions unexpected?  Or, why did they just not take off to begin with?

Oh, believe me, two hours at these latitudes in coastal area during winter is more than plenty to invalidate any weather forecast.

The day after, the replacement flight was a 767. There was no snow on the runway,  but it was still a pretty exiting landing. I think I understand the 777 pilot better now :)

@Tim Did they announce a positive landing?


text:
Is ADS-C used in practice?
Both the FAA and the EASA have decided against using ADS-C in the development of NextGen and SESAR, because of cost, scalability and ease of use. But has ADS-C actually been implemented and used in practice anywhere?

ADS-C is used in oceanic environments, for example over the Atlantic and the Pacific.
FL350 to FL390 on the North Atlantic Track System is restricted to ADS-C equipped aircraft. Non ADS-C aircraft have to fly either below or above those levels (crossing through those levels is permitted)
The text below is a part of today's Norht Atantic Track message issued by Shanwick Center (EGGX):

222021 EGGXZOZX
(NAT-2/2 TRACKS FLS 310/390 INCLUSIVE
MAR 23/1130Z TO MAR 23/1900Z
PART TWO OF TWO PARTS-
E MALOT 53/20 53/30 53/40 53/50 RIKAL
EAST LVLS NIL
WEST LVLS 310 320 330 340 350 360 370 380 390
EUR RTS WEST NIL
NAR NIL-
F LIMRI 52/20 52/30 52/40 52/50 TUDEP
EAST LVLS NIL
WEST LVLS 310 320 330 340 350 360 370 380 390
EUR RTS WEST NIL
NAR NIL-
REMARKS.

TMI IS 082 AND OPERATORS ARE REMINDED TO INCLUDE THE

TMI NUMBER AS PART OF THE OCEANIC CLEARANCE READ BACK.
2. ADS-C AND CPDLC MANDATED OTS ARE AS FOLLOWS
TRACK A 350 360 370 380 390
TRACK B 350 360 370 380 390
TRACK C 350 360 370 380 390
TRACK D 350 360 370 380 390
TRACK E 350 360 370 380 390
TRACK F 350 360 370 380 390
END OF ADS-C AND CPDLC MANDATED OTS

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text:
Where can I get a history of METARs?
Is there a place where past METARs are logged?
Suppose I want all the METAR for a given airport from October 1st to October 15th 2015. Where can I find them?
If it matters, I'm looking in particular for METARs from French airports.

Only source I know of is http://www.aviationweather.gov/dataserver (US primarily, but does seem to have  METARs from around the world). But, it only has access to the past 3 days worth of METARs.

I'm looking forward to reading the answers on this question. One thing I've been looking into lately are METAR trends which can be helpful when reviewing weather for flight planning purposes.

Also worthwhile to check Weather Underground -- they have a pretty good history of METAR reports for the US, and they may for international airports as well.

@mins Ogimet works.

@RalphJ Do you have a link?

The duplicate question has an answer which answers this one, although the original question only asked about airport ceilometer data.  Thanks for asking the question though, as it will enable people in the future to find that one!

The following link is specific to one airport (KJFK) for one particular day, but it shows the repository of Weather Underground METAR reports: http://www.wunderground.com/history/airport/KJFK/2015/10/12/DailyHistory.html?req_city=Kennedy%20International&req_state=NY&req_statename=New%20York&reqdb.zip=11499&reqdb.magic=4&reqdb.wmo=99999&theprefset=SHOWMETAR&theprefvalue=1

@usernumber  I posted a more complete explanation on the question which this one is marked as a duplicate of -- [here] (http://aviation.stackexchange.com/questions/14596/is-there-a-database-of-airport-ceilometer-raw-data/22174#22174)  I actually like THIS question better, but since it points to the other, it's all good, I suppose.

OgiMet Professional information about meteorological conditions in the world is such a site that offers 30-day history for METARs/SPECIs and TAFs reports.
The coverage is said to be worldwide. Here is a glance at the query interface:

The site states these conditions of use for the reports:

About all the codified met. reports (SYNOPS, METAR ...), the copyright
are from every country or source institution. To use them,
read WMO resolution 40.

(essentially it says it's free for use.)
The site accepts requests for up to 31 days at once.
Example: METARs for month of September 2020 for Orly / LFPO:

this website is terrible. no matter how much data I query it fails to return

@usernumber look at the NCEP MADIS archive they have METAR data going back to March 2006.

I find the site works fine but seems not to retain data for as long as one year.  For example today is Dec 4 2020 and this search for data for November 29 2019 failed http://www.ogimet.com/display_metars2.php?lang=en&lugar=KAVK&tipo=ALL&ord=REV&nil=SI&fmt=html&ano=2019&mes=11&day=29&hora=12&anof=2019&mesf=11&dayf=29&horaf=17&minf=59&send=send but one for the same date in 2020 worked fine.  PS perhaps I spoke too soon, after several more searches I just got the message "#Sorry, Your quota limit for slow queries rate has been reached"

@quietflyer: Thanks, I wasn't aware and I get the same message. Related (a METAR decoder using Ogimet source).

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text:
Why don't airlines provide smoke hoods?
In
Fire-involved Accidents and Incidents Reviewed
, Rudolf Kapustin stated in 1993 that

Nearly all aircraft accident fatalities that are not the result of
  crash/impact injuries are the result of post-crash fires and the
  inability to exit aircraft quickly, which in most cases is attributed
  to incapacitation from toxic smoke, fumes or injuries.

This makes me wonder why airlines don't provide smoke hoods for their passengers in case of a fire, the same way they provide life vests in case of a water landing. If flights crossing a body of water must have life vests available for all passengers in case of a water landing, why not make an equivalent law for smoke hoods in case of a cabin fire?
Protective breathing equipment, or smoke hoods are protective head coverings that prevent wearers from breathing the smoke, particulates and toxic gases generated in a fire. There are two main types of hoods: those that have a source of breathable air and those that just filter the particles out of the air.
The smoke hood for aircraft passengers wouldn't need to be a firefighting grade smoke hood, just enough to get everyone out of the plane before they get asphyxiated.
Today, the recommendation in case of a cabin fire is to stay near the ground where the air is more breathable. If passengers could be equipped with smoke hoods, they could walk out instead, which would likely make an evacuation faster.
Granted, the smoke hoods would be used on rare occasions, they have a cost, take up space, weigh something, and you have to explain to the passengers what to do with one in case an accident happens. So it is unlikely that an airline would spontaneously decide to equip all seats with an emergency smoke hood.
But life vests have all of those disadvantages as well. It seems to me that these hoods would not be any heavier or any more expensive than the life vests, and might be used on more occasions than the life vests. I've seen smoke hoods the size of a soda can, so finding a place to fit one on each seat can't be so hard.
So why aren't plane equipped with emergency smoke hoods for passengers?

Your question is very verbose and apparently has several parts of the answer too.

I've been thinking a bit about the question, but everything I can think of points to the fact that it would be better if there were smoke hoods.

@usernumber You are allowed to pose a question and then write an answer to it.  I wouldn't recommend having an answer mixed into your question.

This is a good question overall and one I'd like to see answered, it could use a bit of work though.

@Farhan I don't think it actually contains very much answer. It mentions many factors that would need to be considered in an answer (e.g., efficacy versus various forms of cost) but doesn't attempt to weigh those factors against one another.

@DavidRicherby It could be. I wasn't very excited about the length of this question and requested OP to consider revising it to a less wordy alternative.

Can a passenger carry his own smoke hood. Will it be allowed by FAA / TSA?

Welcome to Amsterdam Airlines!

@Koyovis would you care to expand?

This is an issue on airline passenger safety that has been debated since a very long time, and there are various arguments for and against the use of smoke hoods.
A classic example which showed the requirement for smoke hoods was the British Airtours Flight 28M, which had an engine failure during its take off roll at Manchester International Airport in August 1985. The ensuing fire and black smoke made the evacuation very difficult, and as a result 48 people died from smoke inhalation. Perhaps, the presence of smoke hoods could have saved many more lives. But at the same time, the subsequent investigation revealed there were other factors which contributed to the tragedy, such as the restricted access to exits and standard operating procedures which did not take into account the wind direction before turning.
From what I have read and researched, smoke hoods might involve unnecessary time wasted in wearing them. After all, airline crews are trained to evacuate a passenger aircraft within 90 seconds with half the emergency exits blocked. This time is considered sufficient to escape toxic smoke related fatalities. Secondly, the passengers might require some detail as in how to use them. Surely, space, weight and cost issues are secondary and can easily be overcome, but these are other issues which prevent their use.
In case of a fire upon crash landing, the immediate action is to evacuate and go as far away as possible from the aircraft. Since the passenger will not be staying in the smoke, it does not seem logical to provide smoke hoods. A water landing on the other hand might require passengers to float on the water surface for some time till emergency services arrive. This necessitates the need for a life jacket, otherwise lives can be lost due to drowning.

Basically smoke hoods would make sense for smoke during the flight caused inside by cabin fire. For evacuation only, donning the hood would take too much time. And I guess the oxygen masks could be used to survice with smoke in the cabin until the plane has been taken to the ground.

Factors that airlines are likely to consider

extra cost and weight of equipment
additional time and cost to check equipment regularly

still present after each flight
in good working order regularly

need to instruct passengers
need to supply boarding parents with specialized devices for infants and small children

and provide extra instruction

fatalities may rise due to inevitable incorrect use (example)
what happens when the panicking passenger by the exit puts their hood on back-to-front?
how to introduce intrusive and effective instruction without increasing fear of flying?
Every new airplane model must receive a 90-second evacuation drill certification from the FAA before it can fly. Can this be done wearing hoods?
In what circumstances are flight crew likely to instruct passengers to don hoods?
How likely are passengers to be incapacitated before they can find and complete donning of smoke hoods?

I'd contend that the 90-second evacuation would be unaffected - it only applies to an intact aircraft. If it's going to take you 4 minutes to get off a crashed plane full of toxic fumes, I'd rather have a hood.

A smoke hood could complicate the usage of the oxygen mask and life vest.  Also if constructed from synthetic materials, they need to survive direct flame exposure.  Can trap oxygen from the emergency supply.
Just some issues, that I could add to that list that require mitigation and probably procedural steps also,

Another relevant point is that a fire in a confined space can use up all the oxygen in the air very quickly so, for a hood to be useful, it probably has to include its own oxygen supply. But, now, you've increased the amount of oxygen within the plane's fuselage so the hoods might actually make the fire worse and all the people who would have died from smoke inhalation might just end up dying from burns instead.


text:
Can delamination be detected early?
When a composite structure is hit, the impact causes shockwaves which travel through the structure, and cause delamination. Delamination reduces the strength of the composite structure and may cause the structure to break at a fraction of the load it would have carried before the impact.
Delamination and its ill-effects can be reduced, for instance by adding metal at strategic points of the aircraft. But once delamination occurs, how can it be detected? What measure (if any) have been implemented to detect delamination on aircraft?

The most obvious way is to de-assemble the structure and look inside. This leaves the least amount of doubt.
But there are many ways to do this without destruction.

Ultrasonic: The echo of the ultrasonic ping comes back early (reflection at an inner layer) and in multiple echoes (due to the many boundaries inside the delaminated area). This is easy to do and needs access only from one side, but the interpretation of the signal needs some training.
X-ray, but now you need a receiver at the other side.
Knocking on the surface will help with massive delamination
Eigenfrequency Testing of resonant structures. If the structure is damaged, its stiffness is reduced and so is its eigenfrequency.

And there are even ways to monitor the structure in flight:

You can install microphones internally and let them monitor the crackling due to damage. This allows to spot damage quite precisely when the signal is run through suitable computer software.
Or you put optical fibers into the structure and test whether they still transmit light. This needs quite a lot of fibers and optical terminals, though. When a crack interrupts the transmission, you can time the return of the reflected light pulses and determine the location of the damage quite precisely.

Sorry, @aeroalias, but optical inspection from the outside will only work when damage is extensive. Most damage can not be spotted from the outside with the naked eye.

You're correct. I've clarified in the answer.

There are multiple non-destructive methods to detect delamination in composite materials.

In case the delamination occurs on the surface, it can be easily found by visual inspection. This is the easiest method to detect delaminations; however, this is useful only if the delaminations are visible from the outside (i.e. they are on the surface), which is rarely the case, at-least in aircraft.
Ultrasonic testing- In this method, ultrasonic waves are passed through the surface of the material and the response is monitored. Depending on the condition of the material (whether it has defect or not), the ultrasonic waves behave differently.

Source: cnde.iastate.edu
The ultrasonic method used can be through scan (with the transmitter and reciever on the opposite sides of the part) or pulse echo method, where the transmitter/reciever 'listens' to the ultrasonic sound reflected back from the defect or the other end of the part. There are three main methods of ultrasonic scanning in use:

The A-scan presentation displays the amount of received ultrasonic energy as a function of time.
The B-scan presentations is a profile (cross-sectional) view of the part. Here, the travel time of the sound energy is displayed along the vertical axis and the linear position of the transducer is displayed along the horizontal axis.
The C-scan presentation provides a plan-type view of the location and size of defects.
Tap test, using a coin or an instrumented hammer- This is the most widely used method in the field as it requires minimal instrumentation. However, it requires a trained operator, who can distinguish between the normal and delaminated composite from the sound. Instrumented hammers are also available, where the frequency response of the part can be analyzed for identifying defects.

Source: amumagazine.com

Thermography- Here, an energy source is used to produce thermographic contrast between tthe defect on the part. This is useful in detecting shallow subsurface defects, but is rarely used in field operations.

Infrared thermography Source: seattleinfrared.com

X-Ray radiography (or CT scan in some cases)- This is a very accurate method for detecting internal defects; however, the equipment requirements mean that it is usually used in the place of the OEM, though some field equipment is available for military uses.

Fatigue crack under X-Ray, Source: vidisco.com
There are some other methods like the acoustic emission and lasers, which also can be used for detecting delamination. The table below gives some of the methods used for detecting defects in a manufacturing environment

Source: amumagazine.com

@usernumber Tap test and ultrasonics are widely used by operators. Other methods are used by manufacturers.


text:
Delta wing flow patterns (straight and yawing)
I was wondering the differences between fluid patterns and their consequences when a delta wing is straight and yawed slightly. Thank you.

There are many resources on the web which help to answer this question, but not necessarily very recent ones. Take NACA TN 2674 which shows tufted delta wings, or NACA Research Memorandum L57A30. Replicating the content of those in an answer would indeed need some space, so it will be better to ask a more focused question.


text:
What is the most efficient way to get your instrument rating?
For someone that has recently completed their private pilot SEL, what would be the suggested next steps/process to getting instrument rated as efficiently as possible (both time and money)?

It would be similar to the most efficient way to get your private pilot license.

The fastest path to any rating is intensive training.
If you can take time off from work and do an "accelerated instrument training" program you can probably knock out the rating in less than a month. That AOPA article says 8 days, I've seen a lot of two-week courses advertised.
Note however that there's a difference between being instrument rated and proficient for real-world IFR operations in actual IMC. These courses will almost certainly cram all the knowledge and procedures into your head that are required to get you to pass your instrument checkride, but you may have never flown an approach in actual IMC (if suitable weather doesn't pop up for you to fly in your time will all be simulated under the hood), and because everything is compressed and focused on "passing the test" you may come out of the program lacking the confidence to actually go out and use your newfound rating without doing some additional work with a local CFI (this is a point sometimes raised by pilots who have gone through these accelerated training programs).

you also need to get the written out of the way in advance.

VERY good point about time in actual IMC; if you can get it as part of your instrument rating, DO IT.   The hood can simulate a low ceiling with good visibility (such as stratus clouds w/o precip or fog underneath), but it can't simulate a bad-vis situation such as an ILS to 2000 RVR in an indefinite-ceiling fogbank or having to do a VOR/DME into 800' ceilings and 1.5mile vis in driving rain.

@rbp A few of the two-week courses actually include the written - but I expect those courses require a certain masochistic tendency in order to complete them


text:
How does a small charter operator determine where the centre of gravity is for a given flight?
I was reading an account of the 2001 crash of a charter aircraft carrying the singer Aaliyah and her companions.
Within it there's a summary of the investigation by the NTSB which includes the text 'the maximum allowed gross weight of the aircraft was "substantially exceeded" and that the center of gravity was positioned beyond its rear limit'. (similar material here) .
How should the pilots of small charter aircraft go about establishing where the centre-of-gravity is for a given load of passengers and their luggage ? For airliners there are loading specialists and significant information about the weight of the luggage but how do charters of the type involved in this accident establish what's being carried and how the affects the centre-of-gravity ? Is this something pilots are trained in ? Is each piece of luggage weighed ?

Related: How does a commercial airliner measure its weight/mass? and Do airlines weigh passengers and baggage before loading the aircraft?

Complete non-sequitor: there is a post-apocalyptic novel, written by Peter Heller, titled "The Dog Stars". The protagonist has to fly is '56 Cessna to a remote location in a canyon and take off again. There is almost an entire chapter on how he calculates his CoG to figure out if he can take off again. the description is complete with the tables and graphs he uses. It was fascinating to me.

For every aircraft, a weight and balance form is provided in that aircraft's flight manual and pilot operations handbook (POH). It provides a method for determining the aircraft's weight and position of center-of-gravity. It is often represented as a some sort of graph where the person making the calculations can rather quickly establish the results.
The load-sheet can be prepared by an operations office, ground handling agent or the pilot, but it should always be present in the cockpit and verified by the pilot before commencement of flight.
To determine the overall mass of passengers and cargo, it is often unfeasible to weigh everybody and every piece of cargo, so often standard masses are used. They are average "close enough" values to be used in calculations. If it is obvious to the crew that standard masses are not applicable for a given flight, a different method should be used - like weighing.
The above method may sound rather inaccurate, which it is. Payload makes only about 10-20% of total aircraft weight, so even gross errors in determining mass of passengers and bags usually does not compromise safety.
Usually the reason behind these kind of accidents is poor safety culture within the airline where load-sheets are not prepared at all or they do not even try to represent actual conditions. It is easy to slip in this kind of behavior if the passenger load is always the same like it could be in a chartered business jet with only a few seats. Then comes the day when the plane is full and bags are heavy. In smaller aircraft the cargo hold is usually in the tail, sometimes in the nose. If it is stacked with heavy bags you are most likely outside approved operational envelope.
Also there are several known cases where VIP passengers have put pilots in tough situation and demand that their gear is loaded even if it is obvious that aircraft is overweight. This can be reinforced by the bosses who want to keep their high-paying, high-profile customers happy.

When I was bush flying on floats we used stripes painted on the floats that marked the water line at gross wt/aft cg. "Load lines".  You'd be picking up a load at a remote lake and you could only guess at the weights - maybe I'm over, maybe I'm not.  The load lines did the job as long as the water wasn't too choppy.  I was mildly overweight frequently, but when it got to where the load was obvious, in extreme cases I had to use tricks like faking a takeoff attempt to get the customer to agree to offloading gear without complaining to the boss.  My boss would back me up in the end though.

The sad part, @JohnK, is that you had to trick people into saving their own lives (and yours). Sheeple can be so stupid...

Biggest problem was predecessor pilots the customer knew in the past who would haul anything. "Well, Rusty would carry loads like that all the time". Biggest overload I took was when the lodge owner begged me to take his Indian fishing guide back with me because he seemed to have a tooth abscess.  He was a little guy so I was probably less than150lbs over, in a C-185. As long as the CG is ok, and the lake is long, it's not dangerous, just illegal, and for the right reasons you bend the rules a bit.  Bush flying is a live-by-your-wits profession, and decision making is often shades of grey.

Thanks ! Interesting answer.

Might be worth reflecting that the determination by the investigating agency must also be based on estimates, as much of the baggage and cargo will have been destroyed and redistributed in the crash and any ensuing fire. I get that crash reconstruction can do pretty amazing things but many materials in baggage will simply not survive a fire and can only be guessed at.

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text:
What navigation actions does a pilot take when simply told to "go around"?
In this recording of ATC during the 2008 crash of a British Airways Boeing 777 at London Heathrow the controller is heard to say "Qatari 011, go around".
How would the pilot of Qatari 011 know what actions to take in terms of which direction and level to fly at? Is it assumed that some other controller will direct the traffic to a holding area?

Depending on which country you're flying in, the specific approach may or may not have a defined missed approach procedure.
If the plane is flying a visual approach, then you're most likely not going to have a procedure to use when going around. The generally accepted technique is to either fly the runway heading and climb to a safe altitude, or enter the airport's traffic pattern until ATC gets back to you, but that's generally not a legal requirement.
If the plane is flying an instrument approach, the approach plate will include missed approach procedures. Of course, ATC may give you instructions on what to do if you have to go around, in which case, these instructions take priority.

See my comment on Mike's answer. A visual approach does not have a published missed approach segment.

@ymb1: No one said this aircraft was on a visual approach, but HW said "If the plane is flying IFR... the approach will include missed approach procedures." That is an incorrect statement. A visual approach is an Instrument Flight Rules procedure.

I've reworded my answer to be more general, so it hopefully includes procedures in other countries. Is this better?

There was an incident when a Ukraine Airways flight lined up but didn't take off immediately.   ATC told an approaching plane to go around.  Normally the airspace over the runway would belong to the go-around, and they canceled Ukraine's takeoff clearance for that purpose, but Ukraine did not hear.  So they told the go-around to immediately turn!  Good thing their radio was not also on the fritz.

@HiddenWindshield “almost certainly the case” could use an “except in the US”. We may be an exception, but it’s an important one, and it frequently confuses foreign pilots who may never see a visual approach anywhere else. And don’t get me started on circling or contact approaches!

@StephenS How's that?

@HiddenWindshield In the US, you will usually get a visual approach when the ceiling is above the MVA. Visuals allow less spacing between planes and thus more planes per hour.

Anytime an IFR aircraft, on an IFR approach, does a go-around, there is a published missed approach that must be followed.
(In some jurisdictions an IFR aircraft can be given a Visual Approach clearance and the published missed approach would no longer be valid in the case of a go-around during a Visual Approach).
The published IFR missed approach procedure is the same whether or not it is a pilot initiated or ATC initiated missed approach (go-around).
In an ATC initiated missed approach, the missed approach procedure will be often be amended. If the aircraft is expected to return for landing, ATC may say something like: “Climb runway heading, maintain 5,000’, contact departure”.
In the case of a pilot initiated missed approach, ATC will also often amended the missed approach procedure. The Sometimes the pilot may ask for an amended missed approach during the approach, or during the missed approach.
Amending the missed approach procedure can be useful for maintaining aircraft separation and expediting the flow of air traffic in the area.
If no amendment is given, the aircraft will follow the published missed approach and hold as published.
In this case particular case, “Quatari 011 go around” was followed by “Quatari 011, standard missed approach”.
An example of a Runway 27L missed approach is:  MISSED APCH: Climb STRAIGHT AHEAD, when passing 1080' or D0.0 ILL, whichever is later, climbing turn LEFT on track 150 to 2000'. When passing D6.0 LON climb without delay to 3000', then as directed.
ATC would then give further instructions, or the aircraft would hold at “EPSOM” as published.

"Anytime an IFR aircraft does a go-around, there is a published missed approach that must be followed." — this is patently false; in the USA at the very least, it is made very clear to both pilots and controllers that a visual approach does not have a published missed approach segment. I don't know how things are done in the UK (a quick search was not as helpful as I hoped) but as a blanket statement it is incorrect due to the FAA counterexample.

Also note that the published missed approach for an instrument approach procedure is designed to provide separation from terrain and obstructions, and not necessarily procedural control from other aircraft operating in the area. For this reason it is (again, in the USA) exceedingly uncommon for a published missed approach to be executed at a towered airport; heading and altitude instructions will be provided and the aircraft will be vectored back around for another approach.

@randomhead That is (giving a vector and climb altitude) very common in Europe as well. But the MAP is the default unless specified otherwise. And visual approaches are very rare for IFR traffic, doubly so for airliners.

@randomhead I am not sure about EGLL, as that is an extremely busy airport and surely be stricter, but LKPR has this in the AIP: "2.21.3.1    Visual approach 2.21.3.1.1 Visual approaches are prohibited.", then some exceptions,  and "2.22.4.2.9 The IFR flight conducting visual approach shall, in case of the missed approach, conduct missed approach procedure, which is published on instrument approach chart for the same runway, unless otherwise instructed from the ATC."

@randomhead It is not that the NDB approach MAP is different from the VOR approach MAP and that different from ILS approach MAP. They are the same. If there is no approach plate for the visual approach, the pilot just follows the MAP from one of the other plates. Maybe in some complicated cases they might use ILS backtracking, unavailable for the NDB approach or similar, but in this case they are the same, fly track xxx, climb to 4000 ft, vectoring will be provided. In case of RCF turn right to OKL VOR...

@randomhead I have edited my answer to address Visual Approaches.

Changed to +1! :)

Aircraft on an instrument flight rules flight plan have received a clearance to fly to a specific point and no further; this is called their clearance limit. These days the destination airport is usually the first and only clearance limit for a flight, but this is not necessarily so; an aircraft may be cleared to a certain radionavigation aid or set of coordinates and be told to expect further clearance later. If they reach their clearance limit without receiving further clearance they must initiate holding procedures at that location.
An instrument approach procedure is a combined route and set of altitudes that are designed to allow aircraft to navigate both laterally and vertically to a point where they can acquire visual reference to the runway environment and execute a landing (or, in the case of an autoland approach, to allow them to navigate all the way to the runway itself). As the other answers have said, a missed approach procedure is a part of that approach, and it is designed to allow the aircraft to navigate both laterally and vertically away from the ground and to a safe altitude in the event that, for any reason, a landing cannot be accomplished.
(A visual approach is a procedure where the pilot has the airport [or the runway environment or a preceding aircraft] in sight, and instead of navigating by reference to instruments to the runway they navigate by visual reference out the window. A visual approach has no missed approach segment;1 in the event of a go-around at a towered airport ATC will provide explicit instructions, and at a non-towered airport the pilot is expected to continue to navigate visually and land as soon as possible or else contact ATC for further clearance.)
It is also possible for ATC to issue heading and altitude instructions to a go-around aircraft instead of permitting them to execute the published missed approach. This is often more beneficial if there is other traffic in the area. In the absence of such instructions the pilots should be planning on flying the published missed approach; if for some reason they do not receive ATC instructions and there is no published missed approach, probably it would be safe for them to assume a climb on runway heading to a known minimum safe altitude (or minimum sector altitude) for their area. This minimum altitude is published on the approach chart.
In this specific case, at 1:26 in your linked video the controller issued a go-around instruction to QTR011, which the pilot acknowledged. Later in the video, at 2:20, the pilot queried the controller; I can't quite understand what he said, but it must have been asking the controller to confirm their instructions after completing the go-around, because the controller responded (at 2:23) "Qatari zero-one-one, standard missed approach." This told the pilots that they were to execute the standard, or published, missed approach procedure.

1FAA JO 7110.65 7–4–1

It's also possible to pre-negotiate an alternate missed approach procedure. For example if the published procedure includes a left turn but there is a thunderstorm to the left, a pilot could request something like "Tower, FooAir 1234, in the event of a missed approach, request runway heading due to weather." – "FooAir 1234, Tower, runway heading for missed approach approved as requested".

Either there is a published procedure to follow (usual for controlled airspace) and there will be either company procedures and/or aircraft type specific procedures to follow.
What exactly the crew will do depends on the combination of those. Raise gear (if applicable), apply power, raise flaps (as needed), raise nose (if needed to increase climb rate), and either follow ATC instructions or the published procedures for a new heading and altitude to reconnect to the arrival queue.
Over Heathrow, no doubt there is an established procedure that the crew will have followed for course and altitude to take, as well as speed, until such a time that they're contacted by ATC to guide them into a hold or diversion airport (I'm not sure what the controllers at Heathrow decided after that crash, they could either bring in the arrivals on the single remaining runway, divert them to say Gatwick, or hope the delays won't lead anyone into a fuel emergency and let them circle while the damage is assessed).

authors: Vladimir F Героям слава


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A330 flown by low cost airline - is 8 cabin crew really all they have?
I'm reading the Australian Transport Safety Bureau report on an incident involving an AirAsia X A330 (PDF). The flight in question was intended to be Sydney to Kuala Lumpur so something like a ten to twelve hour flight.
The report mentions that there were 8 cabin crew on board.
Wikipedia says AirAsia has 377 seats in their A330's. Can it be true that they service that many seats with only 8 cabin crew ?

For what it's worth, according to FlightAware, that flight usually takes around 8.5 hours, not 10-12.


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Based on what concept/strategy is a new aircraft ICAO code assigned?
I refer to the official ICAO database.
BOEING  747-8 BBJ   B748    LandPlane   Jet 4   H
BOEING  BBJ (747-8) B748    LandPlane   Jet 4   H

I fail to understand when ICAO assigns a new code, and when not. As an example, I do not see the reason why there are 2 entries (in the database) like the ones above.
In other cases there are no ICAO codes at all, like for the A330-800/900 NEO. So I wonder what process does ICAO use to create a new code. Any idea?


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What does ICAO database "engine count c" mean?
In the official ICAO database 5 aircraft are marked with an engine count C. What is that supposed to mean? Normally engine count is a number (0,1,2,3...).

I don't know the exact ICAO phraseology, but it certainly seems to describe an aircraft that has two engines combined to a single driveshaft.
Soloy has trademarked the 'Dual Pac', a pair of turboprops driving a single shaft through a gearbox. All of the Soloy aircraft there use this powerplant.

The Fairey Gannet was a (super cool) anti-submarine aircraft designed in the late 40s. It was powered by the Armstrong Siddeley Double Mamba which you could argue was the direct predecessor of the Dual Pac, albeit using a presumably very different gearbox to drive the contra-rotating prop. One half of the Double Mamba could be shut down in flight, and both props would continue to be driven:

The Double Mamba engine could be run with one Mamba stopped to conserve fuel and extend endurance for cruise flight. The contra-rotating propellers meant that when only half of the Double Mamba was running there were no thrust asymmetry problems.


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Do I need a stamp for my USPA license?
A few weeks ago I finally finished all of my USPA A license requirements. My instructor signed off the final things and even the card but forgot to put the stamp itself on the form.
I was about to send the form off to get my A license card but am hesitant without the stamp. Do I need the stamp to have it processed? More importantly, will I be able to use my paper form as the temporary A license without the stamp?
I normally wouldnt have an issue just going back to see him, but I am overseas for several months and really wanted to jump when I take leave.
I'm hoping to find an instructor or someone with personal experience with this... Thanks!

I can't answer your question, but the USPA licensing page has a phone number and email address for licensing questions. That should get you an answer if no one here can help you.

I'm a USPA AFF, tandem, and static line instructor.  Your signed and completed A-License Proficiency Card is valid and USPA will process it without the stamp.  You only need the stamp if you want to go to another dropzone and use your card as a temporary license.
The proficiency card is only valid for 60 days after the date it was completed, so don't waste time sending it in.  The last I heard, USPA is taking 3-4 weeks to process license applications.
Edit to add:  Don't send in the actual card.  You can mail a photocopy, fax it in, or scan it and email it to membership@uspa.org.  Faxing or emailing will get you your official license a few days faster.


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How long does it take to get your official FAA certificate in the mail?
I'm asking this question because the only answer on the web right now is pretty old and I assume this is a common question. The above link refers to an FAA page that says:

We are currently processing permanent Airmen Certificates for
  temporary certificates that were issued approximately May 3, 2015.

The above quote hasn't been updated in weeks.
How long does it normally take to get a new certificate in the mail?
Does it vary substantially?
Is there a better place than the above link to get an idea of how long a certificate will take to be processed?

The Airmen Certification page you linked to is the best place to get a quick status update - the little note at the top gets updated when they move into a new batch of certificates. You can also search for yourself in the airmen certification database: When your new certificate or rating shows up there your certificate is probably in the mail.
How long it takes to get your permanent certificate depends mainly on how many they have in the queue ahead of you - Mine took about 60 days, but I've heard as little as 30 and as long as 100+.
If you're getting close to the expiration of your temporary certificate you can request an extension either online or at your local FSDO (more details over on this answer)

It appears that a 'batch' is about 4 weeks long- mine was April 21 to May 10.
It also changed to the next batch in late June, so they are about 7 weeks behind the day, and it took about 7 weeks to process the certificate - at least in my case.

For me, I filed on May 22, 2017 and didn't receive my card until July 24 so it seems to be about 2 months.


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Does Global Entry give you any benefits when flying GA?
If I fly GA into Canada from the US or into the US from Canada, does having Global Entry give me any advantage? Can I taxi straight to the FBO or my tie down spot, or do I still have to taxi over to customs? Is there any ability to fly direct to a destination and not have to stop at a port of entry airport?
What is the difference between Pre clearance and Global Entry? Can you get pre clearance without having Global Entry?

You might try asking this on travel.SE as well; people there may be more knowledgeable about Global Entry

@Pondlife Yeah, they probably have more knowledge about Global Entry, but probably not as much about GA aspects.

CBP has a lot of programs. Government programs are confusing. Regarding the two you mention...
Global Entry basically expedites the Customs process for pre-approved travelers, making use of an automated kiosk. The service is available at approved locations, generally major aiports. ClearlyNormally, this program is meant for the commercial traveler. However, large international GA destinations can have this service as well. Example: FLL, one of the nation's busiest international GA airports. They have a global entry kiosk at their GA facility.
Preclearance means that traveler processing/aircraft inspection are handled before the flight, rather than upon arrival in the US. But, this isn't very widespread yet. Private aircraft preclearance processing is only available at Shannon, Ireland and Oranjestad, Aruba. And the list of airports you can fly to, from what I have seen, is smaller than the list of Ports of Entry.
So no, neither of these programs really helps you out as a Canada/US travelling GA pilot. They aren't for small airports. You have to deal with Customs, APIS, and Ports of Entry, and everything else :)

Great. Thanks for the detailed answer. I was having a lot of trouble finding information on these programs that applied to flying GA. I'll award you the bounty in 18 hours when SO let's me.


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What are the bump outs on a Bell 430 helicopter for?
On a Bell 430 helicopter, you'll see what look like short wings on the side. I've seen people fueling in them, so I assume they are fuel tanks, but do they serve another purpose? Do they have a name?

From pictures you can also see they contain the side landing gear.

Those are called sponsons and serve a few purposes:

In a number of helicopters, they hold the fuel tanks; for example, in Sikorsky CH 53E Super Stallion, the main fuel tanks are in the sponsons. From Sikorsky archives:

The CH-53E main fuel system was contained in the extended length sponsons. Fuel for the No. 1 and No. 3 engines was supplied by a self sealing bladder fuel cell in the sponson.  Fuel for the third engine (No. 2) was supplied by an additional self-sealing fuel cell in both the left and right sponsons.

They also serve as housings for main landing gear
They also serve as mounting points for stores, like external fuel tanks in CH 53E and for mounting torpedoes, as in the CH-148 Cyclone prototype below:

Image from jproc.ca

They are called sponsons and act as enclosures for the retractable main landing gear.  The 430's ancestor, the Bell 222, was equipped with the same fairings.

The 222U did not have retractable landing gear, yet the sponsons remain. That supports the OP's assertion that they serve multiple purposes.


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What is NASR, The FAA's System for Managing Aeronautical Information?
I've googled this question, and know:

The National Airspace System Resource (NASR) System provides the Federal Aviation Administration (FAA) with the means for storing and maintaining a reference database with descriptive details of the National Airspace System's (NAS's) infrastructure and the operational status of all components

But what I'm asking is, what does that mean? Is this where companies like AirNav, Jeppesen, and foreflight get their data? When I update my foreflight database, is it downloading new charts and nav data from NASR, or am I misunderstanding the above quote?
Also, related, when Jeppesen makes their own charts, updates them, etc. are they getting their data from NASR, or somewhere else?

From digging around for a while, I was able to find out that procedures and plates for all airports in the NAS can be found in this large XML file. I haven't been able to find out why approach plates are in a separate XML file, and not in the NASR data, but if anyone is able to give a comprehensive answer to the above question, I'm happy to award a 100 point bounty.

NASR contains the current information upon which Air Traffic Control and other FAA activities depend. NASR supports the management of NAS data used by the FAA, chart producers (including Jeppesen), military and other Government entities to produce a variety of aeronautical publications. Downloads from Foreflight use this data, but may be reformatted to suit the application and would not come directly from any NASR database.
In addition, NASR data is accessed by commercial air carriers, flight planners, and flight systems developers as required by FAA regulation to support the safety-of-flight mission.
The data is available on a 28 day subscription basis. Legacy flat files show the data content, though other forms are available. Definitions for each table are here. The tables are:

Airports and Other Landing Facilities (APT)
ARTCC Boundary Descriptions (ARB)
ARTCC Facilities (AFF)
ASOS/AWOS(AWOS)
ATC Tower and Satellite Airport Communications (TWR)
ATS Non-Regulatory Airways (ATS)
Coded Departure Routes (CDRs) (CDR)
Country Codes
Enroute National Fix Program
Significant Points (NATFIX)
Fix/Reporting Point/Waypoint (FIX)
Flight Service Station Communications Facilities (COM)
Flight Service Stations (FSS)
High Altitude Redesign (HAR)
Significant Points (HARFIX)
Holding Patterns (HPF)
Instrument Landing Systems (ILS/MLS) (ILS)
Location Identifiers (LID)
Miscellaneous Activity Area (MAA)
Military Training Routes (MTR)
Navigation Aids (NAV)
Parachute Jump Area (PJA)
Preferred Route / Tower Enroute Control (TEC) Routes (PFR)
Regulatory Airways (AWY)
Standard Terminal Arrival / Standard Instrument Departure (Complete Set) (STARDP)
State Codes
Standard Terminal Arrival / Standard Instrument Departures (AFSS Subset) (SSD)
Weather Reporting Locations (WXL)


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Can a turbo aircraft be converted to non-turbo?
I'm specifically thinking about the Arrow III. There are hundreds or possibly thousands of turbo Arrow III's, but almost no non-turbos.
Could I buy an Arrow III Turbo (PA-28R-201T) that is at TBO and just put in a non turbo engine? Would it then become a PA-28-201? Can you do that to any aircraft that has a non turbo version as well? For instance, could you convert an Cirrus SR22T to an SR22?

It has been known to happen.  The C320, for example, may be converted to a normally aspirated aircraft by replacing the TSIO-470s with a pair of IO-520s.

In order to do that you would need to have an STC since the aircraft was certified with a turbo. I’ve read a lot about Arrows and don’t recall seeing anything about an STC. A cursory search for the Arrow doesn’t bring up any either. There are certainly none for the Cirrus. However, what many people have done with their Arrow, including the one I fly, is to replace the factory fixed-wastegate turbo setup with  one from Merlyn. The variable wastegate fixes the problems of overboosting with the original and provides about a 5% increase in speed and a higher top altitude.

I think you are wrong on your estimation of the number of non-turbo Arrow IIIs. Checking on Trade-a-Plane I found four turbos and three non-turbos for sale. That matches my recollection of the ratio when we were looking.

You could also draft up some engineering docs and ask for a 337 from your local FSDO. Why you would do this instead of simply buying an NA Arrow is something I'm curious to know. Seems like a lot of expensive and time consuming work only to reduce the performance capabilities of a light SE airplane.

@JScarry if you actually look up the N numbers, you'll see that a lot of the Arrow IIIs on the market are actually turbos, just not advertised as such. There are three non-turbo arrows on the market right now that I know about, one in Switzerland, and two in the US that are about 20k above our flying clubs current budget.

@JScarry also, thanks for the info on Merlyn. I'm looking into it. We're a flying club, so trying to reduce complexity and maximize engine life with many different pilots.


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How are STCs granted for similar aircraft? Archer vs Arrow
I'm specifically interested in the Garmin GFC 500 autopilot certification, but this question can apply to any STC question.
The GFC 500 is certified for a ton of Archer (PA-28) variants, but no Arrow (PA-28R) variants, and Garmin doesn't seem to have any plans to certify the Arrow. Since the Arrow (201) and Archer (181) are the same airframe, the only difference between them is the engine and the landing gear as far as I can tell. Why would the work put into certifying the PA-28-181 not basically cover also certifying the PA-28R-201?
When getting an STC, do you have to start the entire process from scratch for every variant of every aircraft you're trying to get an STC for?

Having been involved with several FAA STC's for GA and airliners I can pass on my experience. Additional FAA information is available in FAR part 21, 23, 125 and here.
First, transport, airliner's, etc are not held to the same rules. The FAA generally considers the engineering department of aircraft manufactures such as Cessna, Boeing or Aerobus to know what they are doing and pretty much rubber stamps anything they come up with. What they are mostly looking for is performance and operational documentation.
[ For 5yrs I was part of a Boeing team that primarily modified doors such as cargo doors for special purposes. We installed and verified or corrected engineering drawings for the modification and approval process. FYI: when I wasn't doing that, I did the final ramp, taxi and opps check of aircraft before their first flight out of Everett WA.]
GA aircraft STC's are administered by the regional FAA office (FSDO) and the process is highly dependent on the region and personal inspector. (The FAA says it's standardized, but it is not.) For example many float planes are flown all the way to Alaska to get approvals because the Anchorage regional office is experienced and generally more permissive than other offices.
Typically the FAA reviews the applicant against new product standards and expects the applicant to provide the "same as" level of safety found in FAR part 21, 23, and 125. With the new "industry self policing" policy passed last year, all bets are off on how it will be done in the future.
I have seen STC's approved with as little explanation as "performs equal to or better than original equipment..." on high performance Alaska Borer props, vortex generators, lights, antennas, gauges, etc with very little or no other data. In 2000, the Alaska FSDO changed from pencil whipping strobes (i.e. ...it works fine on 3000 other Cessna 172's..), to requiring 3 page form that includes a illumination profile chart to be filled out! The A&P's started a revolt and I don't know what happened, I moved three years later to work for Boeing in Seattle.
EXAMPLE: I assisted an Alaska company in a fuselage battery mount. I took a damaged C-180 and removed the tail surfaces and separated the fuselage aft of the cabin. I then hung a 25"G" horz weight (later 7G vertical) from the battery CG for 5min and took a picture. I certified the test and submitted it and received approval. I then took that approval and resubmitted approval for all applicable aircraft with the same skin thickness (individual W&B was calculated for each installation). It took about 6mo for the first approval and an additional year for about 15 additional aircraft to became STC approved. The company estimated it cost around $20-30k.
It often depends on the whim of you local FSDO. One of the reasons Wichita Kansas is a popular place for manufactures is the FSDO office is notorious for ignoring FAR regs. A good example is one FAR says "...every part large enough to be identified must have a unique part or serial number". Try to find a serial or part number on control columns/sticks, rudder peddles, flaps, wings, ribs, bell-cranks, etc. There are AD's on Cessna parts such as gauges but they don't have a part or serial number! An A&P can't write, I complied with the AD by replacing part "x" with new part "y"! (what some A&P's do is use the parts manual number, but the parts manual is not "approved" data by the administrator.)

Very interesting, thanks for sharing!

Thx - I got my job at Boeing for being a Continental ramp maintenance shift supervisor (4ea B757 and 2ea B737 flights per day). When Boeing stopped making the B757 (which I thoroughly loved) I realized I was a "has been" and knew how folks must have felt when the Ford Tri-motor, DC3, or Constellation became out dated.

So what you’re saying is that it totally depends, and that some FSDOs may make it easy to get an STC for a similar aircraft to one that already has an STC, and some FSDOs may require onerous testing be done all over again?

Yes! But that is nothing new. All one has to do is read some of the quagmire AOPA has to deal with on some medical problems. The FAA's long arm is inconsistent. This has been going on for a long time, thats why congress recently passed the "pilots bill of rights". Another area of great consternation is the inconsistent application of AD's and well documented unpunished criminal actions of .some inspectors.


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How to fly a drone in Class D in Italy?
I am traveling for a wedding which will take place in Monza Park, Italy. According to Italian Airspace Pro, the location I would like to fly, the southern half of the park, is technically in Class D airspace, which is restricted unless cleared by ATC.

Click image for full view.
I know that in the United States, the FAA regulations state that to fly in restricted airspace, you must:

Notify the airport and air traffic control tower prior to flying within 5 miles of an airport*

Is flying within restricted airspace possible if I contact a local tower there? Who would I need to contact?

Btw, those requirements in the US are no longer in place; different ones are.

Don't confuse "controlled" airspace (such as class D) with "restricted" areas. They are two different things.

The class D airspace you are referring to is a control zone (CTR). According to article 24 of Regulation for Remotely Piloted Aerial Vehicles, the following applies to VLOS operations (emphasis mine):

Except as required by point 6 below, RPAS operations shall not be conducted:

a) within ATZ and beneath take-off and landing paths or at a distance less than 5 km from the airport (ARP or published geographical coordinates) where ATZ is not established;
b) within CTR, without prejudice to point 5 below;
c) within active restricted areas and prohibited areas.

Operations within CTR are permitted only to RPA with operating take-off mass less than 25 kg, up to maximum height of 70 m AGL and within maximum horizontal distance of 200 m. Beneath take  off  and  landing paths, beyond ATZ boundaries and up to 15 km from  the airport, maximum height shall be 30 m AGL.

When  operations  do  not  meet  the  requirements set  forth  in  points  4a), 4b) and  5 above, operations shall be  carried  out  according  to  procedures  published  by  ENAC. When it  is required to operate within airspace as referred in point  4c) above,  operations  shall  be subject to specific authorization according to procedures published by ENAC.

Although you are pretty much directly below the approach path to Linate's runway 18, since the park is just over 15 km from the airport, you should be OK to fly up to 70 metres above ground as long as the drone stays within 200 metres of you.
Of course, there are also other applicable rules to consider: for example, you must wear a high vis vest with "Pilota di RPA" printed on it, you are not allowed to overfly crowds (including wedding guests) and the drone must be registered and identifiable.

I know this is an old question and OP has probably long left Italy again. Still think it deserves a proper answer, though.

Contact Italian aviation authorities to make sure (probably their ministry of transportation).
They'll be able to tell you what permits and licenses you need (if it's possible at all).

According to my Foreflight, it is ground to 2,000 feet.  Also, in is attached to LIML airport Linate-Milan.  Look up the tower/Approach telephone number when you arrive.


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Do F-22's use cartridge start to start engines?
What method does the F-22 use to start its engines?
In the video below, you can see a flap open and flame and steam shoot out as the engine starts to spin up.  Is this an example of cartridge start?  If so, could anyone explain how this works in greater detail?
Video of F-22 engine start:

No, the F-22 has an Allied Signal APU in the port wing root opposite of the cannon installation, which is on the starboard wing root.
From GlobalSecurity.org (http://www.globalsecurity.org/military/systems/aircraft/f-22-fcas.htm)
Auxiliary Power Generation System (APGS)
The Auxiliary Power Generation System (APGS) for the F-22 is being developed, built, and tested by Allied Signal Aerospace for Boeing. The APGS consists of an auxiliary power unit (APU), and a self-contained Stored Energy System (SES).
The APGS provides secondary aircraft power for everyday main engine ground start, aircraft ground maintenance, and in-flight emergency power for aircraft recovery. The APGS uses the G-250 APU, a 450 hp turbine engine that utilizes state-of-the-art materials and design resulting in the highest power density APU in the industry (horsepower-to-weight).
It is possible the APU uses a cartridge to start it up, as opposed to electrical power.  The video you posted is good evidence of that.

F-15s and F-16s use nitrogen pre-charged hydraulic start systems.  There is no 'air' involved.  The utility hydraulic system pumps fluid into the two accumulators against the nitrogen side of the chamber.  When the handle is pulled for starting, NORMALLY one bottle is opened and the hydraulic fluid is released thru the hydraulic start motor on the JFS.  After engine start, the hydraulic fluid is replaced under pressure.  If both bottles are expended, there is a hand pump for the purpose of refilling the bottles - NOT THE PREFERRED METHOD!!!!  In super cold weather, the use of both bottles together may be required.


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At what point is a turbine powered ducted propeller considered a turbofan?
Turboprop Propellers can be ducted for extra thrust.  What are the criteria for determining that the engine is no longer a ducted propeller design, but a turbofan? Does there have to be a type of blade design, a fully separate nacelle/pod, number of blades?  Or are all turbofans technically shrouded propellers with some augmented thrust from the turbine exhaust ?

I would say when it uses exhaust gas as the primary source of thrust rather than a propeller.

@RonBeyer Doesn't most thrust in a turbofan come from the fan?

@Steve For a high-bypass turbofan, yes, for a low-bypass, no. I guess the distinction may be what is driving the fan at the front. Usually a ducted fan doesn't have any thrust from the exhaust gas, whereas a turbofan combines the two.

The fan is the first rotor of the engine compressor, in addition of being a ducted propeller accelerating the bypass flow. So a fan is part of the turbine engine.

I would argue there is no definitive answer. Each engine manufacturer has their own definition of what common components mean. Example NGV vs SGV. As far as I'm aware there is no standard for naming of things.

@Notts90  Is there not a generally accepted engineering or industry wide definition of what constitutes a turbofan?  Just a bit curious.

@NZKshatriya there are many descriptive words that are ambiguous in aviation, particularly turbine engines. The manufacturers like to make up/merge words to describe new things which doesn't help. Another example of the industry not agreeing names it made up is open rotor vs propfan.

@Notts90  That answers my question.  I have a strong interest n aviation/aviation history, but I come from a computer hardware background, where there are concrete definition for different things, say, CPU architecture (where a CPU may be considered a systems engine)  hence why I asked.  Never been a fan of manufacturers making their own terminology.

@Notts90 I do believe you mean now posted and not "not" posted lol.

Related: https://aviation.stackexchange.com/questions/27300/how-does-a-fan-differ-from-a-propeller

tl;dr
They're pretty much all considered turbofans with a few exceptions from the '70s such as this experimental Britten-Norman Islander. They key difference is a prop can be considered a separate entity (add-on) to the turbine for a turboprop, but a fan is an integrated component for a turbofan.

Slightly longer answer
After a fair bit of thought and research I hope I've managed to come up with a satisfactory answer, though to start with a disclaimer. The aviation industry is far too fond of merging and creating new words to describe new engine architecture. Take Open Rotor vs. PropFan for example.
To get technical about it, you could look at the similar/reverse argument about the difference between an open rotor turbofan and a turboprop, as addressed by the EASA.
If you look at Appendix 1: Open Rotor Definition (Page 86) of that document they outlined the following key differences

Open rotor module that cannot be distinguished as a separate entity

However the following was the agreed definition, which is still rather ambiguous.

A Turbine Engine featuring contra-rotating fan stages not enclosed within
  a casing

I think the first one is more key, the prop can be considered as a separate entity, attached to the front of a turbine and powered by a gearbox. A fan is an integral part of the engine and cannot really be considered a separate entity, as it actually forms part of the low pressure shaft and is considered the first stage of the low pressure compressor.

Maybe the engine designation is determined by the tail number. It seems quite fitting in this case. :)

I would say that would'nt definitely be a turbofan if there is no mechanical linkage between the "turbojet" section (the gas generator) and the turbine driving the propeller. But this would be just my own definition of what isn't a turbofan.

In general (there are often exceptions to any rule), a turboprop unit is likely to have a gearbox between the turbine and the propeller. The propeller is likely to be capable of varying its pitch. Also, the propeller may be a set of two contra-rotating propellers in the case of a high power turboprop. A turbofan engine is unlikely to have these features, although PW does have a GTF geared turbofan.

We don't see many contra-rotating turboprops around, actually.

The Tu-95/Tu-114 and the An-70 are the only two (three) that I can think of, indeed.

The difference between a ducted propeller and a turbofan is mainly determined by the difference between a propeller and a fan.

A propeller has relatively few blades, which are relatively long and slender.
A fan has many blades, with a relatively large chord. Like a household fan.

A parameter to catch blade count and chord relative to blade length, is the disk solidity $\sigma$. Area of all blades summed together, divided by the area of the circle defined by the blade tip length:
$$\sigma = \frac{\text{blade area}}{\text{disk area}} = \frac{A_b}{A} = \frac{N_b c R}{\pi R^2} = \frac{N_b c}{\pi R}$$ with $N_b$ = number of blades, c = blade chord, R = blade radius.
Image source
There does not seem to be a defined transition point of $\sigma$, above which we're talking about a fan. The 8-bladed propeller of the A400M with a blade radius of 2.6m has a solidity ration of about 0.3 which is amongst the highest in the world. We instantly recognise it as being a propeller.
Author 1
The fan of a geared turbofan like the PW 1000G is instantly recognisable as a fan, with its 20 relatively fat blades and a $\sigma$ close to 1. Note that both are driven by a gearbox for obtaining a beneficial tip speed.

Or are all turbofans technically shrouded propellers with some augmented thrust from the turbine exhaust ?

Indeed, technically a fan is a type of propeller. Turboprops also have thrust directly from the turbine exhaust.

1 By Rafael Luiz Canossa - IMG_9975, CC BY-SA 2.0, https://commons.wikimedia.org/w/index.php?curid=55662586

Great answer (+1) though I think the comparison to a household fan is confusing.


text:
How quickly could a commercial airline integrate advances in technology into its fleet?
How quickly would a commercial airline be able to integrate significant advances in technology into its fleet?
Specifically I am interested in large commercial airlines and advances in technology that would substantially increase the efficiency of fuel consumption in passenger aircraft, but I don't have enough of a background in commercial aviation to make an educated guess and have not been able to find a comparable historical example. If someone could provide me with either it would be much appreciated.

This is a difficult question to answer because it depends what the 'magic bullet' actually is and how the airframe, engines and/or avionics have to be modified. The 787 had a lot of new materials and technology and just certifying it apparently took 8 years.

The times of significant advances ended half a century ago. Now any advance is incremental; however, given the lifetime of a modern transport aircraft of 30 years, it does accumulate over such a long time.

Many good questions generate some degree of opinion based on expert experience, but answers to this question   will tend to be almost entirely based on opinions, rather than facts, references, or specific expertise.

@DannyBeckett I do not agree, maintenance and replacement are well documented activities. You can argue that is too broad, but I can hardly see how this question invites opinions.

It depends on the advance. Generally, there are three ways how airliners can be improved:

Operations and procedures: This can be as simple as faster turn-around times so aircraft will be more profitable, or as complicated as doing away with airways which would help to shorten trips, but depends on changes in regulations which have been in place for decades.
Better equipment: All parts of an aircraft are designed to be individually replaceable, and swapping old engines for newer, more fuel efficient ones will bring already two thirds of the efficiency benefits of replacing the whole aircraft. Other examples could be less heavy furnishings or more precise instruments. But there are limits, and every change needs to be approved by regulatory authorities.
Newer aircraft models: This brings aerodynamics, engines and equipment up to the status quo, and is done by airlines on a regular basis to improve both their attractiveness and their profitability. Examples are Singapore Airlines, which pride themselves on an average age of their fleet of just seven years, or Vueling, which thanks to a recent expansion has lower seat-mile cost than all their competitors.

Generally, the days of dramatic technology advances are long gone. Today, years of research are justified by single-digit percentage advances, and a new development like the A380 is started with a promise of just 15% less seat-mile cost when compared to airliners which are two decades old by the time the new plane is put into service.
To answer your question directly: Changes which produce meaningful improvements need years of preparation and testing for approval by the authorities. Quick gains are not possible anymore.

If pressed (each plane is grounded until it is installed)? As fast as it's maintenance guys can pump them out per plane.
Doing so would require getting the plane to the shop and having the mechanics installing the "advance" which could take a few days. They would then also take the chance to do some of the regular checks.
If not then the install would be scheduled along with the other regular check already planned in its lifetime depending on how labour intensive the installation is.
Before all that can actually happen the guys doing the install must be trained and the supervisors must be able to certify the installation, that will also take time.

I think the regulatory approval from the FAA, EASA etc. will take a lot longer than the installation

Immediately in some cases.
In general, a large carrier will have a heterogeneous fleet in which the most recently purchased aircraft will be more performant and fuel efficient than the older aircraft. A carrier can generally "buy" fuel efficiency simply by selling older airframes and buying new ones with new engines.
Another way carriers can improve fuel efficiency is by how they load the airframe. Seats and other fixtures onboard are removable and the carrier can reconfigure aircraft in various way and improve the way the equipment is constructed to make it lighter. Carriers are always looking for upgrades that will lighten the load or balance the load better to improve fuel efficiency.
There are also computational ways to fly more efficiently. For example, if the flight plan and route planning can make use of winds aloft more efficiently significant fuel savings can be realized. Advanced software can also be used to tune engines or fly the aircraft so that engines use fuel more efficiently.

Buying a new aircraft is hardly "immediate". According to Wikipedia, if you order a current-model Boeing 737 today, you're at the back of a waiting list of over 1500 planes. At the moment, they're building about 400 planes a year, so that equates to a 3-4 year wait.

I would try to give some structure to the answer. Firstly, take into account that any technological innovation on the airplane itself it is not performed by the airline, is done by the airplane manufacturer like in car industry.
For giving you a more concrete answer I would divide in three:

Only renewing improving the fleet by a new one. A way to get the latest technology is just by selling to other airlines or transport companies the old models and buy new airplanes. Typical life span of a airplane is aroud 20-30 years, so that will be how often airlines do that.
Another way is implementing retrofits, airplane manufactures offer some improvements as retrofit of the airplane like the A320 sharklet. However you need a business case, not all retrofits are implemented because they are not interesting, apart from the cost of buying from the manufacturer the retrofit the airline will have the airplane in ground during the retrofit. Usually to maximize the business case the airline waits until a complete overhaul (revision) is perform on the airplane to take the advantage is already grounded.
Finally: as soon as possible. Just take a look to the recent battery issues on B787 airplanes were grounded during a long period to avoid reducing safety standards. When this kind of situations happen, airlines try to implement technology changes (or just modifications) as soon as possible. Business case is really possitive...

Finally, I think the right question is... who pays the modification in the last situation?


text:
Can commercial airliners fly over central Antarctica during winter?
For example, if an airline decided they wanted to run year round flights on the great circle from Perth to Buenos Aires with a commercial airliner (e.g. A380 or B747), would they be able to do so? Or would it be too cold to fly?
I'm aware that there are a few sightseeing flights during the summer over Antarctica, but the winter temperatures in central Antarctica are lower than anywhere else on Earth (with surface air temperatures occasionally reaching around −90 degrees Celsius).
Edit: To clarify, by "winter" I mean the coldest time of year, i.e. roughly May to September.

Related: What's required for a plane certified to fly to Antarctica?

Also related: https://aviation.stackexchange.com/q/939/1467

Both poles are in use these days: https://en.wikipedia.org/wiki/Polar_route

@Floris I meant the actual winter (roughly May to September), i.e. the coldest time of year.

I just did SCL to SYD (QF28) and we flew over Antartica, and on the way back it was AKL to SCL (LA800), and we flew across the ocean instead.

Surface air temperatures aren't really going to be relevant for an airliner. The temperature of the troposphere doesn't vary that much. In fact, the troposphere is warmer at the poles (from Wikipedia Troposphere):

At middle latitudes, tropospheric temperatures decrease from an average of 15 °C at sea level to about −55 °C at the tropopause. At the poles, tropospheric temperature only decreases from an average of 0 °C at sea level to about −45 °C at the tropopause. At the equator, tropospheric temperatures decrease from an average of 20 °C at sea level to about −70 to −75 °C at the tropopause.

Sightseeing flights are indeed run during the summer months, but that is because it's actually possible to see things, not because it's any warmer. It wouldn't be very interesting to do a sightseeing flight in darkness.
The biggest obstacle to doing winter commercial flights over Antarctica is the lack of suitable alternate places to land in the event of an emergency.

"[...] in the event of an emergency." - Aren't aviation laws so that the commercial airlines would also be responsible for ensuring the safety of their passengers? As in there'd be the additional logistical twist of needing to cart e.g. very warm blankets around in the event of a crash landing in polar territory.

@DenisdeBernardy: See Do airlines have contingency plans to keep passengers warm in the event of an Arctic emergency landing (or otherwise a diversion)?

The troposphere extends from the ground to only about 23000ft at the poles. So any aircraft flying over the polar regions is going to be well above the troposphere.

@DenisdeBernardy You need to land first.  Ice is not very forgiving.

IIRC, Mt. Erebus was tried once as an alternative site.  It didn't go well.

"The biggest obstacle to doing winter commercial flights over Antarctica is the lack of suitable alternate places to land in the event of an emergency." Isn't the alternative a whole bunch of ocean? Not exactly a great landing place either.

@DavidRicherby: Flight levels are pressure altitude. Passenger flights don't get anywhere outside the troposphere.

"... event of an emergency" - so how do sightseeing flights get past the requirement of having places to land during an emergency?

@Esteemator: By careful planning, during the summer, when the ice runways are open, and there are facilities available to house passengers if something goes wrong.

@GregHewgill: Umm, yes, they do.

They could, if only they were allowed to.
From

§ 121.161 Airplane limitations: Type of route.
(a) Except as provided in paragraph (e) of this section, unless
  approved by the Administrator in accordance with Appendix P of this
  part and authorized in the certificate holder's operations
  specifications, no certificate holder may operate a
  turbine-engine-powered airplane over a route that contains a point—
(1) Farther than a flying time from an Adequate Airport (at a
  one-engine-inoperative cruise speed under standard conditions in still
  air) of 60 minutes for a two-engine airplane or 180 minutes for a
  passenger-carrying airplane with more than two engines;
(2) Within the North Polar Area; or
(3) Within the South Polar Area.

However, AC 120-42 contains a rationalle on minimum range operations, and explains that twin engine range restrictions started a long time ago, and that turbine engine technology is now so reliable that number of engines is not the limiting factor anymore. From 202 b.:

All long-range passenger-carrying airplanes, regardless of the number of engines, needed a viable diversion airport in the case of onboard fire, medical emergency, or catastrophic decompression. Ensuring availability of en route alternate airports, adequate fire fighting coverage at these airports, and fuel planning to account for depressurization are sound operational practices for all airplanes, including three- and four-engine airplanes.

And AC 120-42 202 mentions that it may be possible for airlines to cross the Antarctic region in the following circumstances:

c. Those areas not supported within 180-minute diversion authority tend to be routes over remote areas of the world that are uniquely challenging to the operation. These areas include the South Polar Region, a small section in the South Pacific, the southern South Atlantic Ocean between South America and Africa, the southern Indian Ocean and the North Polar area under certain winter weather conditions. The additional operational challenges of these routes are equally demanding of all airplanes, regardless of the number of engines, and include such issues as extremes in terrain and meteorology, as well as limited navigation and communications infrastructure. Support of a necessary diversion and subsequent recovery in such areas demands added training, expertise, and dedication from all certificate holders.

I could not find any direct flights from Australia to Buenos Aires, all go via New Zealand or further. And those flights would avoid the shaded areas on the map I would imagine.

This answer has looked at the flight path of a Qantas flight from Sydney to Santiago, which uses Tahiti as a diversion airport. A flight over Tahiti is much more northern:

The route shown in the answer here does not seem to avoid it completely https://aviation.stackexchange.com/q/939/1467 (the flight would be much longer)

@Federico That's a great answer, have included a reference to it.

Flat-Earthers would soo smell a conspiracy in these regulations ;)


text:
What are the advantages/disadvantages of placing an engine in the tail?
What are the advantages and disadvantages of having an engine in the vertical stabilizer, a la the DC-10, Lockheed TriStar, and 727?
It seems that this has gone out of fashion among jetliners. Is there a reason for this?
It seems that the FAA's 60 Minute Rule was an impetus for the trijet configuration. But is that the only motivation? Is a tail engine less aerodynamically efficient?

A guess: satisfies the certification requirement with the fewest number of engines?  Why use four when three will do?  And if you're going to use three it makes sense that one must be along the centerline of the airplane.

Think of all that structure that has to hold that engine up. Think about how tall the tail has to be. Extra hydraulic and fuel lines, etc. Then add in the incident of Flight 232. Now take into consideration that newer engines are much more efficient, powerful, and reliable than the older engines. It "went out of style" because it just isn't needed.

Just a nit, but in the interest of possible extreme accuracy, the L-1011 and the 727 might better be thought of as having the engine in the fuselage rather than the vertical stabilizer. The engine air intakes were at the base of the vertical stabilizer and fed S-ducts that delivered the air to the engine in the fuselage. The DC-10 and the follow on MD-11 had straight-through air flow, thus avoiding S-duct problems.

Partial duplicate and Related

As you write, at the time those trijets were designed they enjoyed preferential treatment over aircraft with two engines for overwater operation. They also were more efficient than comparable designs with four engines. See here for that discussion.
However, the wing-mounted engine has some advantages:

Flutter damping when mounted ahead of the elastic line of the wing
Bending relief
Easier access for maintenance
Shorter fuel lines

The tail position was chosen because three engines were enough for the optimum size of those airliners and equipping them with four engines had lowered efficiency. If you need to put three engines on an aircraft, one has to be in the line of symmetry, and here the best compromise was on or in the rear fuselage. Had more powerful and reliable engines been available back then, you can be sure they would had used only two engines and mounted them on the wing. But we had to wait two more decades until turbofan engines were powerful enough and the certification authorities were convinced of their reliability.
The fashion of early jets to put all engines at the back was just that and had ended before the trijets were designed.

I have a question on that bending relief "engines provide bending relief on the wing, allowing better wing design (thinner wings): less drag". Putting engines under the wing requires reinforced wings, right? That would make wings likely bigger? So I assume we have generally bending on the wing because it creates (more) lift than the heavy center-body/cabin and the engines-pods put a downforce on the wing, which reduces this beending to some degree?

@Peter: No, the wing creates lift and can lift the heavy engines directly. If the engines were mounted on the tail, that portion of lift would need to be carried all the way to the wing root and the back of the fuselage, requiring a heavier structure. The static case (where the wing has to carry the weight without creating lift) is trivial - a wing fit for flight will have no trouble carrying the engine on the ground.

Ah. Okay, make sense :)


text:
What are these FAA facilities in Seattle doing?
While walking in Discovery Park I discovered this radar dome with FAA notices on its fence.

And not far away I cam across this small FAA signed radio antenna and shack.
Any idea what these facilities do?
My guess would be the radar is used by Seattle Center and that the small antenna is a marker beacon for southbound approaches to SeaTac.

This is one of those questions that gives me the national security creeps.

Does that mean I should take it down?

The antenna does look like a MB antenna and it may be a decommissioned MB for Rwy 14 at BFI. It's about 8 NM from the threshold, but it's pure conjecture on my part. There are no navaids currently showing on any charts in that location. The only thing I could find in that area is the Fort Lawton RCO for Seattle Center (127.05 MHz).

"national security" doesn't depend on hiding RADAR sites, which (of course) must transmit to be effective.  RADAR is easily detectable by anyone who cares.

Location of the second photo is adjacent to the Ursula Judkins viewpoint - https://goo.gl/maps/WfXFahfrt7p

I lived in Seattle for 20+ years, and used to fly R/C gliders near that radome.  At that time (early 1980s), the local glider fliers were convinced it was still active; if you flew near it, you were very prone to radio glitches (the kind of thing you'd get from harmonic interference by a high power off-frequency beam).  Thirty-five years later, it still appears to be maintained.

Seattle’s "golf ball" in Discovery Park was once part of the country’s Nike Hercules air defense system of missiles and radars in the 1950s. While most of the structures have been torn down, this golf ball still stands as a relic of the Cold War.
Discovery Park used to have an array of radars at its peak. It was a Nike Ajax air defense site in 1953 before becoming an Air Force command center for the Nike Hercules system. The remaining radome was built in 1959. It is not currently in use.

https://blog.seattlepi.com/thebigblog/2013/04/09/what-is-that-giant-golf-ball-in-seattle-sky/#photo-226558

Initially assigned a Permanent ID of RP-1 and later a Sage ID of Z-1. Abandoned by the Air Force in 1963 and turned over to the FAA, now known as Fort Lawton FAA Radar Site.

https://seattlediscoverypark.org/faa-tower/

More information:

https://en.wikipedia.org/wiki/Project_Nike

First picture is the Air Route Surveillance Radar (ARSR-1E) located at Fort Lawton (source 1, source 2).
The second picture is the NOLLA NDB (long overhead wires) along with an outer marker beacon (dual Y-arranged Yagi antennas). These two used to serve the localizer approach into Boeing Field's 13R (now 14R).

The first picture is the Fort Lawton FAA Radar Site, an active high power long range CARSR RADAR providing data for USAF/NORAD Battle Control System-Fixed (BCS-F) operations centers (EADS & WADS) as well as the FAA Seattle ARTCC (ZSE) and adjacent ARTCCs as well as Homeland Security.  It operates between 1.2 and 1.4 GHz at a -minimum- peak power of 50000 watts, the fence is standing far away from the transmitting antenna for a reason-it's dangerous.